This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Approximately 2% of the U.S. population is chronically infected with hepatitis C virus (HCV). Chronic HCV infections result in significant liver disease, including cirrhosis and liver cancer in approximately 20% of infected individuals. The current therapy of interferon and ribavirin does not result in viral clearance in the majority of cases. The development of improved antiviral strategies to treat HCV chronic infection is essential for the control of this disease. The objective of this study is to test a series of small molecule antiviral inhibitors of HCV replication for efficacy in chimpanzees chronically infected with HCV. The study has examined antiviral activity from several different classes of inhibitors, and each of the classes has been examined in both PK and efficacy studies.